Nearby star may explain sunspot ‘gap’ on our star

On average, sunspot appearances occur in 11-year cycles, but our Sun has faced a 70-year low-activity “hiatus” without them, at an unusual period in its history. Now, a nearby star (out of 58 studied) is undergoing the same hiatus, giving experts the opportunity to study it and, who knows, determine the reasons that led to our own star’s seven-decade silence.

Starspots – and sunspots, for that matter – are dark marks that appear on the surface of stars due to the sudden drop in temperature in the affected area, resulting from the process that creates their electromagnetic field (called “dynamo”). In the case of the Sun, astronomers have been studying the frequency of occurrence of these events since the 1600s, when they were first observed by the mathematician and philosopher Galileo Galilei.


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Example of sunspots on the surface of the Sun: Event tends to be cyclical, but period of low activity that occurred centuries ago still intrigues scientists (Image: DeepSkyTX/Shutterstock)

Because we’ve been studying the subject for so long, we have a pretty consistent certainty of this 11-year period, with the exception of the so-called “Maunder Minimum”, in the early 1700s, where 70 years without sunspots have left experts adrift – we have no idea what led up to it, basically. And this is not us talking, but the astronomers themselves:

“We don’t really know what caused the Maunder Minimum, and we’ve been looking at other Sun-like stars to see if they offer any insights,” said Anna Baum, a graduate student at Penn State University and primary author of a new study. on topic. “We were able to identify a star that we believe has entered a state similar to the Maunder Minimum. It will be very exciting to continue to look at this star during and hopefully when it comes out of that period, as this can be extremely informative about the activity of the Sun 300 years ago.”

Analyzing data from six decades of starspots on 59 stars, Baum and his team compiled a database of bodies that appeared simultaneously in several of their sources, in addition to making efforts to standardize measurements from different telescopes to compare them directly and avoid errors. of calculation.

The conclusion: 29 of the 59 stars analyzed have observable sunspot cycles, all lasting more than a decade. Others didn’t make it to this list simply because they were spinning too slowly to have a dynamo or were essentially “dead”, nearing the end of their lives.

“This 50-plus-year ongoing series allows us to see things we would never have noticed within the 10-year intervals we were observing before,” said Jason Wright, professor of astronomy and astrophysics at the college and co-author of the study. “Interestingly enough, Anna found a promising star that had been cycling for decades, but apparently stopped.”

The star in question is called “HD 166620” and the team estimates an average starspot cycle of 17 years, but which now appears to have gone into low activity, without showing any spots since 2003. Initially, Anna and her team thought it was a a miscalculation, such as a typo in one of the sources used in the investigation. After checking and confirming everything, however, there was the realization that the timeline of these events was consistent, making this star an ideal object for research.

The idea now is to continue observing HD 166620 in order to determine the origin of these gaps and, with luck, to know if the conclusions can be applied to the sunspots of our own star.

The full paper can be accessed in the Astronomical Journal.

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